System defining a hybrid power unit for thrust generation in an aerial vehicle and method for controlling the same

Abstract

One variation of a system for generating thrust at an aerial vehicle includes: a primary electric motor; a rotor coupled to the motor; an internal-combustion engine; a clutch interposed between the motor and an output shaft of the internal-combustion engine; an engine shroud defining a shroud inlet between the rotor and the internal-combustion engine, extending over the internal-combustion engine, and defining a shroud outlet opposite the rotor; a cooling fan coupled and configured to displace air through the engine shroud; and a local controller configured to receive a rotor speed command specifying a target rotor speed, adjust a throttle setpoint of the internal-combustion engine according to the target rotor speed and a state of charge of a battery in the aerial vehicle, and drive the primary electric motor to selectively output torque to the rotor and to regeneratively brake the rotor according to the target rotor speed.

We claim: 
     
       1. A hybrid power unit for a vertical-takeoff-and-landing aircraft, the hybrid power unit comprising:
 a primary electric motor; 
 a rotor having a rotor rotation rate and configured to generate a rotor-generated vertical lift thrust for the vertical-takeoff-and-landing aircraft, wherein the primary electric motor is drivingly coupled to the rotor; 
 an internal-combustion engine; 
 a clutch interposed between the internal-combustion engine and the rotor, wherein the clutch is reconfigurable between an engaged configuration and a disengaged configuration, wherein the internal-combustion engine is drivingly coupled with the rotor via the clutch when the clutch is in the engaged configuration, and wherein the internal-combustion engine is drivingly decoupled from the rotor when the clutch is in the disengaged configuration; and a local controller configured to:
 receive a rotor speed command specifying a target rotor rotation rate for the rotor; 
 in response to a target state of charge for a battery of the vertical-takeoff-and-landing aircraft exceeding a state of charge of the battery, select a battery charging throttle set point for the internal-combustion engine for outputting an engine torque by the internal-combustion engine, wherein the engine torque has a magnitude selected to accommodate transmission of a first portion of the engine torque to the rotor to drive rotation of the rotor at the target rotor rotation rate and transmission of a second portion of the engine torque to the primary electric motor for generation of energy by the primary electric motor; and 
 operate the internal-combustion engine at the battery charging throttle set point; and 
 while the internal-combustion engine is operated at the battery charging throttle set point, control the primary electric motor to generate energy at a variable rate that controls a magnitude of the second portion of the engine torque transmitted to the primary electric motor from the internal-combustion engine so that the first portion of the engine torque transmitted to the rotor from the internal-combustion engine maintains the rotor rotation rate at the target rotor rotation rate. 
 
 
     
     
       2. The hybrid power unit of  claim 1 , further comprising a first pulley rotationally coupled with the primary electric motor, a second pulley rotationally coupled with the rotor, and a drive belt rotationally coupling the first pulley and the second pulley, wherein the internal-combustion engine is drivingly coupled with the second pulley via the clutch when the clutch is in the engaged configuration, and wherein the internal-combustion engine is drivingly decoupled from the second pulley when the clutch is in the disengaged configuration. 
     
     
       3. The hybrid power unit of  claim 1 , further comprising a cooling fan having a cooling fan rotation rate and configured to be operable to generate a cooling airflow for cooling the internal-combustion engine, wherein the cooling airflow generates a cooling fan generated lift thrust for the vertical-takeoff-and-landing aircraft, wherein the cooling fan generated lift thrust is oriented to augment the rotor generated lift thrust, and wherein the local controller is further configured to:
 determine a target total thrust corresponding to the target rotor rotation rate; 
 determine a target cooling fan rotation rate for the cooling fan based on a temperature of the internal-combustion engine; 
 estimate a magnitude of the cooling fan generated lift thrust generated via operation of the cooling fan at the target cooling fan rotation rate; 
 determine the target rotor rotation rate based on the target total thrust and the magnitude of the cooling fan generated lift thrust. 
 
     
     
       4. The hybrid power unit of  claim 1 , wherein the local controller is further configured to:
 receive a second rotor speed command specifying a second target rotor rotation rate for the rotor that is less than the target rotor rotation rate; 
 select a second throttle set point for the internal-combustion engine based on the second target rotor rotation rate, wherein the internal-combustion engine outputs a second engine torque at the second throttle set point that is less than the engine torque at the battery charging throttle set point; 
 in response to receiving the second rotor speed command, control the primary electric motor to generate energy via regenerative braking to reduce the rotor rotation rate to the second target rotor rotation rate over a first time interval and control the primary electric motor to maintain the rotor rotation rate at the second target rotor rotation rate over a second time interval following the first time interval; and 
 control the internal-combustion engine to operate at the second throttle set point to reduce output of the internal-combustion engine from the engine torque at the battery charging throttle set point to the second engine torque at the second throttle set point over a combined time interval that includes the first time interval and the second time interval. 
 
     
     
       5. The hybrid power unit of  claim 1 , wherein the local controller is further configured to:
 receive a second rotor speed command specifying a second target rotor rotation rate for the rotor that is greater than the target rotor rotation rate; 
 select a second throttle set point for the internal-combustion engine based on the second target rotor rotation rate, wherein the internal-combustion engine outputs a second engine torque at the second throttle set point that is greater than the engine torque at the battery charging throttle set point; 
 in response to receiving the second rotor speed command, control the primary electric motor to output torque to the rotor to increase the rotor rotation rate to the second target rotor rotation rate over a first time interval and control the primary electric motor to maintain the rotor rotation rate at the second target rotor rotation rate over a second time interval following the first time interval; and 
 control the internal-combustion engine to operate at the second throttle set point to increase output from the internal-combustion engine from the engine torque at the battery charging throttle set point to the second engine torque at the second throttle set point over a combined time interval that includes the first time interval and the second time interval. 
 
     
     
       6. The hybrid power unit of  claim 1 , wherein the local controller is further configured to:
 in response to the state of charge of the battery exceeding the target state of charge of the battery, select a battery discharging throttle set point so that operation of the internal-combustion engine at the battery discharging throttle set point outputs a combined torque to the rotor, wherein the combined torque comprises torque output by the internal-combustion engine and torque generated by the primary electric motor. 
 
     
     
       7. The hybrid power unit of  claim 1 , further comprising a clutch actuator controllable by the local controller to reconfigure the clutch from the engaged configuration to the disengaged configuration and from the disengaged configuration to the engaged configuration, and wherein the local controller is further configured to:
 receive, while the clutch is in the engaged configuration, a second rotor speed command specifying a second target rotor rotation rate for the rotor that is greater than the target rotor rotation rate; and 
 in response to receiving the second rotor speed command, control the clutch actuator to reconfigure the clutch from the engaged configuration to the disengaged configuration to decouple the internal-combustion engine from the rotor and control the primary electric motor to output torque to the rotor to increase the rotor rotation rate to the second target rotor rotation rate over a first time interval. 
 
     
     
       8. The hybrid power unit of  claim 7 , wherein the local controller is further configured to:
 control the clutch actuator, following the first time interval, to reconfigure the clutch from the disengaged configuration to the engaged configuration to recouple the internal-combustion engine with the rotor; and 
 control operation of the internal-combustion engine, following the first time interval, to output torque to the rotor for rotation of the rotor at the second target rotor rotation rate. 
 
     
     
       9. The hybrid power unit of  claim 1 , further comprising a clutch actuator controllable by the local controller to reconfigure the clutch from the engaged configuration to the disengaged configuration and from the disengaged configuration to the engaged configuration, and wherein the local controller is further configured to:
 detect a failure of the internal-combustion engine; and 
 in response to detecting the failure of the internal-combustion engine, control the clutch actuator to reconfigure the clutch from the engaged configuration to the disengaged configuration to decouple the internal-combustion engine from the rotor and control the primary electric motor to output torque to the rotor to drive rotation of the rotor. 
 
     
     
       10. The hybrid power unit of  claim 1 , further comprising a clutch actuator controllable by the local controller to reconfigure the clutch from the engaged configuration to the disengaged configuration and from the disengaged configuration to the engaged configuration, and wherein the local controller is further configured to control the clutch actuator to reconfigure the clutch from the engaged configuration to the disengaged configuration to decouple the internal-combustion engine from the rotor and control the primary electric motor to output torque to the rotor to drive rotation of the rotor during landing of the vertical-takeoff-and-landing aircraft. 
     
     
       11. The hybrid power unit of  claim 1 , wherein the local controller is configured to control the primary electric motor to generate energy at the variable rate by controlling a voltage and/or commutation to the primary electric motor.